Bamboo‐Based Carbon Fiber/Carbon Nanosheet Composite Flexible Supercapacitor

The primary factors affecting the performance of supercapacitors are ion diffusion, storage, and electron conduction. A unique composite structure combining elongated carbon fibers and void‐filling carbon nanosheets can simultaneously enhance ion diffusion, storage, and charge conduction. Herein, bamboo fibers treated with delignification are used as raw materials. Through a simple chemical delignification process, followed by compression into sheets and carbonization, elongated carbon fiber/carbon nanosheet composite structures are prepared. Supercapacitors made with symmetric electrodes from these bamboo‐based composite materials exhibit a specific capacitance of 97.2 F g⁻¹ at a current density of 0.25 A g⁻¹. The bamboo‐based composite sheets demonstrate excellent flexibility and conductivity due to the stacking of carbon fibers and carbon nanosheets, forming abundant layered voids and a 3D network structure. This layered 3D network structure endows the PVA/H₃PO₄ gel electrolyte with excellent permeability. The bamboo‐based carbon fiber/carbon nanosheet composite interdigitated flexible solid‐state supercapacitor achieves an areal capacitance of 10.59 mF cm⁻² at a current density of 5 μA cm⁻² and retains 0.99 mF cm⁻² even at 200 μA cm⁻². After undergoing various folding angles and 200 folds, the CV curves of the interdigitated flexible solid‐state supercapacitor show minimal changes in shape and enclosed area, demonstrating excellent flexibility and folding durability.